我的服务器运行 MySQL 5.5.40 & 我目前有一个触发器，它首先检查两个日期列(discount_start 和discount_end)是否均为 NULL 或两者都有日期，然后检查discount_start 是否大于discount_end，其想法是确保开始日期不晚于结束日期。
第一位有效，但第二位检查开始日期是否晚于结束日期似乎不起作用。我已经进行了一些 Google 搜索，看来这里允许使用 > 运算符？
我使用的日期时间是discount_start的2015-12-10 04:16:34和disocunt_end的日期时间是2015-12-08 04:16:38，我编写的触发器如下。
# Both discount_start & discount_end must either be entered or NULL, one cannot be NULL while the other is entered
IF NEW.discount_start IS NULL AND NEW.discount_end IS NOT NULL THEN
signal sqlstate '45000' set message_text = 'discount_end has value but discount_start NULL, both need to have a value or be NULL';
ELSEIF NEW.discount_start IS NOT NULL AND NEW.discount_end IS NULL THEN
signal sqlstate '45000' set message_text = 'discount_start has value but discount_end NULL, both need to have a value or be NULL';
# discount_start date must be before discount_end
ELSEIF NEW.discount_start > NEW.discount_end THEN
signal sqlstate '45000' set message_text = 'discount_start must be before discount_end';
ELSE
SET new.created = NOW();
END IF
最佳答案
尝试
... ELSEIF DATEDIFF(NEW.discount_end, NEW.discount_start) < 0 THEN ...
触发代码中允许使用关系运算符(<、> 等)，因此我假设您在 google 上搜索的答案专门指比较 DATE 类型。
关于MySQL 触发器开始日期早于结束日期，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/34080877/